/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.execution.operator.schema;

import com.google.common.util.concurrent.ListenableFuture;
import org.apache.iotdb.db.mpp.execution.operator.Operator;
import org.apache.iotdb.db.mpp.execution.operator.OperatorContext;
import org.apache.iotdb.db.mpp.execution.operator.process.ProcessOperator;
import org.apache.iotdb.tsfile.read.common.block.TsBlock;
import org.apache.iotdb.tsfile.read.common.block.column.BinaryColumn;
import org.apache.iotdb.tsfile.read.common.block.column.TimeColumn;
import org.apache.iotdb.tsfile.utils.Binary;
import org.apache.iotdb.tsfile.utils.ReadWriteIOUtils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.List;
import java.util.Optional;

public class SchemaFetchMergeOperator implements ProcessOperator {

    private final OperatorContext operatorContext;
    private final List<Operator> children;
    private final int childrenCount;

    private int currentIndex;

    private boolean isReadingStorageGroupInfo;

    private final List<String> storageGroupList;

    public SchemaFetchMergeOperator(
            OperatorContext operatorContext, List<Operator> children, List<String> storageGroupList) {
        this.operatorContext = operatorContext;
        this.children = children;
        this.childrenCount = children.size();

        this.currentIndex = 0;

        this.isReadingStorageGroupInfo = true;

        this.storageGroupList = storageGroupList;
    }

    @Override
    public OperatorContext getOperatorContext() {
        return operatorContext;
    }

    @Override
    public TsBlock next() {
        if (isReadingStorageGroupInfo) {
            isReadingStorageGroupInfo = false;
            return generateStorageGroupInfo();
        }

        if (children.get(currentIndex).hasNextWithTimer()) {
            return children.get(currentIndex).nextWithTimer();
        } else {
            currentIndex++;
            return null;
        }
    }

    @Override
    public boolean hasNext() {
        return isReadingStorageGroupInfo || currentIndex < childrenCount;
    }

    @Override
    public ListenableFuture<?> isBlocked() {
        return isReadingStorageGroupInfo || currentIndex >= children.size()
                ? NOT_BLOCKED
                : children.get(currentIndex).isBlocked();
    }

    @Override
    public boolean isFinished() {
        return !hasNextWithTimer();
    }

    @Override
    public void close() throws Exception {
        for (Operator child : children) {
            child.close();
        }
    }

    private TsBlock generateStorageGroupInfo() {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        try {
            // to indicate this binary data is database info
            ReadWriteIOUtils.write((byte) 0, outputStream);

            ReadWriteIOUtils.write(storageGroupList.size(), outputStream);
            for (String storageGroup : storageGroupList) {
                ReadWriteIOUtils.write(storageGroup, outputStream);
            }
        } catch (IOException e) {
            // Totally memory operation. This case won't happen.
        }
        return new TsBlock(
                new TimeColumn(1, new long[]{0}),
                new BinaryColumn(
                        1, Optional.empty(), new Binary[]{new Binary(outputStream.toByteArray())}));
    }

    @Override
    public long calculateMaxPeekMemory() {
        long childrenMaxPeekMemory = 0;
        for (Operator child : children) {
            childrenMaxPeekMemory = Math.max(childrenMaxPeekMemory, child.calculateMaxPeekMemory());
        }

        return childrenMaxPeekMemory;
    }

    @Override
    public long calculateMaxReturnSize() {
        long childrenMaxReturnSize = 0;
        for (Operator child : children) {
            childrenMaxReturnSize = Math.max(childrenMaxReturnSize, child.calculateMaxReturnSize());
        }

        return childrenMaxReturnSize;
    }

    @Override
    public long calculateRetainedSizeAfterCallingNext() {
        long retainedSize = 0L;
        for (Operator child : children) {
            retainedSize += child.calculateRetainedSizeAfterCallingNext();
        }
        return retainedSize;
    }
}
